1. Field of the Invention
The present invention relates to the improvement of a liner for a floppy disk jacket.
2. Prior Art
The floppy disk used for data processing in computers is generally protected with a hard case jacket molded from ABS resins or a jacket formed of vinyl chloride resins provided with a liner on the inside thereof.
The importance of the liner is very great in respect of avoiding the abrasion or damage of the disk surface and of cleaning the disk surface, and a variety of liners have hitherto been proposed.
For example, U.S. Pat. Nos. 4,586,606 and 4,610,352, and Japanese Patent Application Kokai (Laid-open) No. 61-258057 propose liners in which a non-thermoplastic fiber such as rayon and cotton is provided onto the surface which contacts with the disk to obtain a liner construction little abrasive to the disk, and a thermoplastic fiber such as low melting point polyester fiber and nylon 6 fiber is provided to the intermediate layer and is partially thermo-compression-bonded to maintain the fabric strength of the liner.
The basic idea of the prior art method mentioned above is to prevent the formation of abrasion dust of the liner due to its contact with the disk and thus eliminate the disturbance of information transmission at the read-write head of the disk drive of a computer, and for this purpose a non-thermoplastic fiber is provided onto the surface which contacts with the disk to obtain a liner structure little abrasive to the disk. The crucial problem of liners of above prior art is that they are poor in form stability.
The "form stability" referred to herein not only means the ability to maintain a tensile strength required in providing the liner to a jacket formed of vinyl chloride resin or ABS resin, but also involves the form stability in various environments (temperatures and humidities) in which the floppy disk is used in practice, and the form stability to dimensional creep developed when a nonwoven fabric is cut under a tension and then the fabric is released from the tension.
When the liners of prior art are viewed from such points, they are very poor in form stability in various environments. The change in form due to environment (i.e. temperature and humidity) specifically means such physical change as the shrinkage or elongation in longitudinal or lateral direction, or the increase or decrease in thickness, of the liner. When the shrinkage in longitudinal or lateral direction of a liner occurs for example in a jacket for a 3.5" floppy disk, it will press down the lifter (a part which plays a very important role in maintaining the rotatory torque and in cleaning) fitted to the jacket of the floppy disk, causing an abnormal lowering of torque and decrease of cleaning effect, which is an important function of a liner, and thus greatly impairs the function of the floppy disk. Conversely, when the elongation of a liner occurs, it will cause the contact of the liner with the disk at other parts than the lifter part, leading to an abnormal increase of torque. In the case of 8" or 5.25" floppy disks, the dent or the collapse of the jacket will occur owing to the difference in shrinkage (or difference in elongation) between the vinyl chloride resin jacket and the liner.
The change in thickness of a liner also causes similar results. Although the stability of a liner to environmental changes is thus of great importance, no consideration whatever has been given to this point in the liner design of the prior art.